Changing patterns in tongue, oral cavity, laryngeal and hypopharyngeal squamous cell carcinomas in New Zealand: Incidence, trends and survival from 2006 to 2022.

BACKGROUND: Cancers of the oral cavity, larynx, and hypopharynx have traditionally been associated with common risk factors such as tobacco and alcohol use. With changes in smoking and drinking patterns, the incidence of these cancers is expected to change. Although the incidence of oral cavity cancer has been reported recently, there is limited evidence available for laryngeal and hypopharyngeal cancers in New Zealand (NZ). Furthermore, while growing evidence suggests increasing incidence of tongue cancer among females and young individuals, this trend has not been investigated in NZ. This study will therefore assess the incidence rates, trends in incidence, and survival of tongue, other oral cavity, laryngeal and hypopharyngeal cancers. METHODS: The study included patients with a primary diagnosis of squamous cell carcinoma (SCC) oral tongue, other oral cavity, larynx and hypopharynx, which were retrieved from the National Cancer Registry from 2006 to 2022. Directly age-standardised incidence rates were calculated, using the World Health Organisation standard population. Time trends were analysed with joinpoint regression to identify annual percentage changes (APCs), and overall and relative survival rates were estimated. RESULTS: The average annual incidence rate per 100,000 population was 1.2 for oral tongue SCC, 1.0 for other oral cavity SCC, 1.1 for laryngeal SCC, and 0.3 for hypopharyngeal SCC. Males consistently showed a higher incidence rate than females for all tumours except oral tongue SCC, where the incidence rates in older-aged females were higher than that of their male counterparts. Incidence rates differed by ethnicity, with Pasifika having higher incidence rates for oral tongue and other oral cavity SCC, and Māori for laryngeal and hypopharyngeal SCC, compared to European. Over the past 17 years, trends in incidence rates of laryngeal SCC declined significantly with 5 % per year overall and across all sexes, age groups and ethnic groups, whereas those of oral tongue, other oral cavity and hypopharyngeal SCC remained stable. Both overall and relative survival rates were highest for oral tongue SCC and lowest for hypopharyngeal SCC. The 5-year relative survival rates were 73 % for oral tongue SCC, 58 % for other oral cavity SCC, 67 % for laryngeal SCC and 42 % for hypopharyngeal SCC. In addition to age effects, survival outcomes varied by ethnicity, with notable disparity observed among Māori for other oral cavity and laryngeal SCC. CONCLUSION: This study confirms a consistent decline in laryngeal SCC incidence rates in New Zealand over the last 17 years. However, no such decline was observed for oral tongue, other oral cavity, and hypopharyngeal SCC. The findings suggest that the risk attributed by common risk factors such as smoking may vary between tumour sites and demographic groups, particularly for oral tongue SCC.